Production of acetals



Patented May 7,1935 2,000,252

UNITED STATES. PATENT OFFICE PRODUCTION OF ACETALS Walter Reppe and Karl Baur, Ludwigshafen-onthe-Rhine, Germany, assignors to I. G. F81, benindustrie Aktiengesellschaft, Frankfort-onthe-Main, Germany No Drawing. Application January 5, 1931, Serial No. 506,745. In Germany January 23, 1930 14 Claims. (Cl. 260-149) The present invention relates to the production the temperature should not be allowed to rise conof acetals. siderably above 200 C. or even above 100 C.

We have found that valuable products which Since the acetals are all more or less readily hitherto could not be prepared or could only be hydrolyzed, especially in the presence of aqueous prepared with difficulty are obtained in a simple acid agents, their preparation is generally carried 5 manner and in excellent yields by adding alcoout while excluding water asfar as possible.

hols containing more than one carbon atom in the The acetals obtainable according to the present molecule and free from carboxylic groups onto invention are suitable as solvents or softening vinyl ethers. The term alcohols is meant to inagents in so far as they have a suflicient stability clude monoand polyhydric, aliphatic open chain to the action of water. Some of the acetals are 1 or cycloaliphatic alcohols, aliphatic-aromatic aluseful for pharmaceutical purposes. cohols and phenols free from carboxyl groups. The following examples will further illustrate The alcohols must be free from carboxyl groups the nature of this invention, but the invention is since otherwise no acetals might be obtained. not restricted to these examples. The parts are The reaction may be accelerated by the addiby weigh 15 tion of small quantities of accelerators especial- Example 1 1y of acid reacting agents such as mineral acids, halides of mineral acids, acid salts or organic hal- A very small amount of concentrated sulphuric ogen p unds apa of splitting off h n acid is added to '74 parts of butanol. 72 parts ydracids, r als n utral a t f d sir d at leof vinyl-ethyl ether are then allowed to flow in 20 vat d t p atu s a at a p su a v while stirring, the temperature preferably not atmospheric p s with the addition Of being allowed to exceed 30 C. After the converinert organic solvents and diluents, such as of the sion is completed, the whole is stirred for some yp of ethyl ether 0 chloroform, a quantity time, a little potassium carbonate is added and of the alcohol-employed exceed t q d the liquid is decanted oil and distilled. The 25 for the reaction. acetaldehyde-ethyl-normal-butyl acetal corre- By adding the alcohols to the vinyl ethers, acesponding to the formula tals are obtained; the possibility of forming mixed acetals by this method is especially interesting. a The conversion proceeds according to the follow- 011 -011 30 ing generalequation: 0 C4Ho and having a boiling point of from 151 to 152 C. is obtained in a yield of about 60 per cent of 1 R1 RI 0R4 the theoretical yield. The same product may 35 also be prepared in the presence of a less active in which R1 and R2 signify alkyl, aryl or aralkyl accelerator,. such as glacial acetic acid and the groups or hydrogen atoms and R3 and R4 signif like, at higher temperatures and under pressure. alkyl, aryl or aralkyl groups, It can also readily be obtained by adding ethyl 40 The reaction may be readily carried out by alcohol onto vinyl-normal-butyl ether (obtain- 40 simply mixing the components, if desired while able from sodium n-butylate and vinyl chloride) accelerating it by the addition of small quantities or from normal-butyl (a-chlorethyl) -ether by of the aforesaid accelerators, Mineral acids have conversion with sodium alcoholate. a very energetic accelerating action, so that the v reaction may be easily carried out at temperaw p 2 45 tures between -30 and +30 0.; if, however, only a very small addition of mineral acid is used, 80 pa t Of y -ct y to which 2 Pa or if less active accelerators such as phenols, in of ethyl-(u-chlorethyl)-ether have previously the case of adding on alcohols which are not been d, a e allowed to d p w While phenols or salts as for example calcium chloride, tirri g, nt a Solution o 90 Parts Of Phenol in 50 are employed, higher temperatures will be neces- 50 parts o y e yl ther. The reaction temsary both for initiating the reaction and for comperature is kept at about 15 C. by external coolpleting it; in the latter case working in a closed ing. A 10 per cent aqueous solution of caustic vessel is sometimes necessary on account of high soda is then stirred in and the ethereal solution volatility of certain vinyl ethers. In most cases is separated and dried with the aid of calcium 55 chloride. 'The acetaldehyde-ethyl-phenyl acetal corresponding to the formula oH-on 0-C|H1 which boils at from 83 to 84 C. at 10.5 millimetres mercury gauge, is obtained in a yield of from to per cent of the theoretical yield. The same acetal is obtained, but in smaller yields, from anhydrous ethyl alcohol and vinylphenyl-ether with the employment of sulphuric acid as the accelerator.

Example 3 80.5 parts of ethylene chlorhydrin are mixed with 50 parts or ethyl ether and 0.5 part of mmnyl chloride is added and 75 parts of vinyl ethyl ether are then introduced into the mixture while stirring, the temperature being kept at 15 C. by external cooling with ice and water. After some time from 50 to parts of a 10 per cent aqueous caustic soda solution are stirred into the reaction mixture, the aqueous layer is separated and the remaining solution is dried with the aid of calcium chloride. By distillation in vacuo the mixed acetaldehyde-ethyl-2-chlorethyl-acetal corresponding to the formula oar-0n O-C;H Cl which boils at from 53 to 56 C. at 10 millimetres mercury gauge is obtained in a yield of about 50 per cent of the theoretical yield. If desired, the reaction may be carried out at a higher temperature in a closed pressure-tight vessel in which case, however, the yield of mixed acetal is reduced and higher quantities of acetaldehyde di-ethyl acetal are obtained together with acetaldehydedi- (2-chlorethyl) -acetal.

Example 4 62 parts of ethylene glycol are slowly added, while stirring to a mixture of parts of vinyl ethyl ether, 50 parts of ethyl-ether and 4 parts of ethyl-(a-chlorethyl) -ether, the reaction mixture being then further worked up as described in the foregoing example. Symmetrical di-(acetaldehyde-ethyl) -1.2-ethylene acetal corresponding to the formula one-o on O-OIHt-O 6B: is obtained in a yield of about 50 per cent oi! the theoretical yield; the said acetal boils at 97 C. at 13 millimetres mercury gauge.

Example 5 pure cholesterol from which latter the product is differentiated by its considerably higher solubility in ligroin. By a treatment with dilute mineral acids cholesterol is split of! from the product which corresponds to the formula o-om. Q

OHr-O (R=cholesterol) What we claim is:-

1. The process for the production oi acetals, which comprises reacting an alcohol, containing more than one carbon atom in the molecule and free from carboxyl groups, with a vinyl ether while excluding water as far as possible.

2. The process for the production of acetals, which comprises reacting a monohydric alcohol, containing more than one carbon atom in the molecule and free from carboxyl groups, with a vinyl ether while excluding water as far as possible.

3. The process tor the production of acetals, which comprises reacting a polyhydric alcohol free from carboxyl groups with a vinyl ether.

4. The process for the production of acetals which comprises reacting a phenol tree from carboxyl groups with a vinyl ether while excluding water as far as possible.

5. The process for the production of acetals, which comprises reacting an alcohol containing more than one carbon atom in the molecule and free from carboxyl groups with a vinyl ether in the presence of a small quantity of an accelerator.

6. The process for the production of acetals, which comprises reacting an alcohol containing more than one carbon atom in the molecule and free from carboxyl groups with avinyl ether while heating and at a pressure above atmospheric pressure but while excluding water as far as possible.

'7. The process for the production of acetals, which comprises reacting an alcohol containing more than one carbon atom in the molecule and free from carboxyl groups with a vinyl ether in the presence of an inert organic solvent while excluding water as far as possible.

8. The process for the production of acetals, which comprises reacting an alcohol containing more than one carbon atom in the molecule and free from carboxyl groups with a vinyl ether, while heating in the presence of a small quantity of an acid reacting substance while excluding water as far as possible.

9. As new articles of manufacture ethylidine acetals corresponding to 0B: lh-ClEk-O in which R1 and R2 denote hydrogen or alkyl,

aryl or aralkyl groups and R3 and R4 denote hydrocarbon radicles of the alkyl, aryl or aralkyl series diiferent from each other and at least 'one of which containsmore than 5 carbon atoms.

more than one carbon atom in the molecule and free from carboxyl groups, with a vinyl ether at the general iormula' a temperature between about 15 and about 30 C., while excluding water as far as possible.

12. The process for the production of acetals which comprises reacting an alcohol, containing more than one carbon atom in the molecule and tree from carboxyl groups, with vinylethyl ether, while excluding water as far as possible,

13. The process for the production vo1 acetals which comprises reacting an aliphatic monohydric alcohol, containing more than one carbon atom in the molecule and tree from carboxyl groups, with a vinyl ether, while excluding water as far as possible.

14. The process for the production of acetals which comprises reacting an aliphatic monohydric alcohol, containing more than one carbon atom in the'molecule and free from carboxyl groups, with vinylethyl ether, while excluding water as far as possible.

WALTER REPPE.

KARL BAUR. 

